The most common and most likely answer to this crossword clue is the 8 letter word MINIMISE
I've seen this crossword clue in Financial Times
M
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N
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M
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Buddy explains!

The straight part
We know that "To make light of" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to make light of = minimise.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does MINIMISE mean?
MINIMISE verb- To make (something) as small or as insignificant as possible.
- To remove (a window) from the main display area, collapsing it to an icon or caption.
- To treat (someone) slightingly.